Acute promyelocytic leukemia

Hidden abnormalities and novel classification of t(15;17) acute promyelocytic leukemia (APL) based on genomic alterations

Acute promyelocytic leukemia (APL) is a hematopoietic malignant disease characterized by the chromosomal translocation t(15;17), resulting in the formation of the PML-RARA gene. Here, 47 t(15;17) APL samples were analyzed with high-density single-nucleotide polymorphism microarray (50-K and 250-K SNP-chips) using the new algorithm AsCNAR (allele-specific copy-number analysis using anonymous references). Copy-number-neutral loss of heterozygosity (CNN-LOH) was identified at chromosomes 10q (3 cases), 11p (3 cases), and 19q (1 case). Twenty-eight samples (60%) did not have an obvious alteration (normal-copy-number [NC] group). Nineteen samples (40%) showed either one or more genomic abnormalities: 8 samples (17%) had trisomy 8 either with or without an additional duplication, deletion, or CNN-LOH (+8 group); and 11 samples (23%) had genomic abnormalities without trisomy 8 (other abnormalities group). These chromosomal abnormalities were acquired somatic mutations. Interestingly, FLT3-ITD mutations (11/47 cases) occurred only in the group with no genomic alteration (NC group). Taken together, these results suggest that the pathway of development of APL differs in each group: FLT3-ITD, trisomy 8, and other genomic changes. Here, we showed for the first time hidden abnormalities and novel disease-related genomic changes in t(15;17) APL.

Retinoids, rexinoids and their cognate nuclear receptors: character and their role in chemoprevention of selected malignant diseases

BACKGROUND

Retinoids, rexinoids and their biologically active derivatives are involved in a complex arrangement of physiological and developmental responses in many tissues of higher vertebrates. Both retinoids and rexinoids are either natural or synthetic compounds related to retinoic acids that act through interaction with two basic types of nuclear receptors belonging to the nuclear receptor superfamily: All-trans retinoic acid receptors (RARalpha, RARbeta, and RARgamma) and retinoid X receptors (RXRalpha, RXRbeta and RXRgamma) as retinoid-inducible transcription factors.

AIM

Summarization of selected effects of biologically active natural or synthetic retinoids and rexinoids and their exploitation in chemoprevention of various types of cancer.

RESULTS

Retinoid receptors play a role as ligand-activated, DNA-binding, trans-acting, transcription-modulating proteins involved in a general molecular mechanism responsible for transcriptional responses in target genes. They exert both beneficial and detrimental activity; they have tumour-suppressive activity but on the other hand they are teratogenic. A number of nuclear receptor selective retinoids and rexinoids, have been successfully tested using a variety of cell lines or animal models. Retinoids inhibit carcinogenesis, suppress premalignant epithelial lesions and tumour growth and invasion in a variety of tissues.

CONCLUSIONS

Natural and synthetic retinoids exert important biological effects due to their antiproliferative and apoptosis-inducing effects. They are also known to cause redifferentiation or to prevent further dedifferentiation of various tumour tissues.

Immunohistochemical expression of promyelocytic leukemia body in soft tissue sarcomas

BACKGROUND

The function of promyelocytic leukemia (PML) bodies is not well known but plays an important role in controlling cell proliferation, apoptosis and senescence. This study was undertaken to analyze the clinical significance of PML body expression in primary tumor samples from malignant fibrous histiocytoma (MFH) and liposarcoma patients.

METHODS

We studied MFH and liposarcoma samples from 55 patients for PML bodies. Fluorescent immunostaining of PML bodies was performed in the paraffin-embedded tumor sections.

RESULTS

PML body immunostaining was identified in 63.9% of MFH and 63.2% of liposarcoma samples. PML body expression rates of all sarcoma cells were 1.5 +/- 1.8% (range: 0-7.0) in MFH and 1.3 +/- 1.4% (0-5.2) in liposarcoma samples. PML body expression (p = 0.0053) and a high rate of PML body expression (p = 0.0012) were significantly greater prognostic risk factors for death than the other clinical factors in MFH patients. All liposarcoma patients without expression of PML were disease free at the end of the study.

CONCLUSION

Our study suggests that the presence of PML bodies may indicate a poor prognosis for MFH and liposarcoma patients.

Retinoic acid syndrome: a review

The retinoic acid syndrome (RAS) is an unpredictable but frequent complication which may develop after administration of all-trans retinoic acid (ATRA) most commonly in patients with acute promyelocytic leukaemia (APL). In this review, we describe the incidence, predictive factors, clinical course, outcome and treatment of RAS in patients with APL treated with ATRA. The incidence of RAS in patients receiving ATRA is about 14-16%, with an associated mortality of about 2%. Initial high white blood cell (WBC) count, rapidly increasing WBC count and/or the presence of the CD 13 expression on leukaemic cells may help in identifying patients likely to develop RAS. Concurrent chemotherapy will probably decrease the risk of developing RAS but often exacerbates bleeding, leading to leucocytosis, thrombocytopenia, disseminated intravascular coagulation and fibrinolysis. Prophylactic steroids are not recommended but prompt administration of steroids at the first sign of unexplained dyspnea, fever, weight gain or pulmonary infiltrate, is critical. Liposomal ATRA is being investigated to induce haematological cure in APL without chemotherapy and to reduce the incidence of RAS but further validation of its usefulness is necessary.

Drug development against metastasis-related genes and their pathways: a rationale for cancer therapy

It is well recognized that the majority of cancer related deaths is caused by metastatic diseases. Therefore, there is an urgent need for the development of therapeutic intervention specifically targeted to the metastatic process. In the last decade, significant progress has been made in this research field, and many new concepts have emerged that shed light on the molecular mechanism of metastasis cascade which is often portrayed as a succession of six distinct steps; localized invasion, intravasation, translocation, extravasation, micrometastasis and colonization. Successful metastasis is dependent on the balance and complex interplay of both the metastasis promoters and suppressors in each step. Therefore, the basic strategy of our interventions is aimed at either blocking the promoters or potentiating the suppressors in this disease process. Toward this goal, various kinds of antibodies and small molecules have been designed. These include agents that block the ligand-recepter interaction of metastasis promoters (HGF/c-Met), antagonize the metastasis-promoting enzymes (AMF, uPA and MMP) and inhibit the transcriptional activity of metastasis promoter (beta-Catenin). On the other hand, the intriguing roles of metastasis suppressors and their signal pathways have been extensively studied and various attempts have been made to potentiate these factors. Small molecules have been developed to restore the expression or mimic the function of metastasis-suppressor genes such as NM23, E-cadherin, Kiss-1, MKK4 and NDRG1, and some of them are under clinical trials. This review summarizes our current understanding of the molecular pathway of tumor metastasis and discusses strategies and recent development of anti-metastatic drugs.

Translational control of c-MYC by rapamycin promotes terminal myeloid differentiation

c-MYC inhibits differentiation and regulates the process by which cells acquire biomass, cell growth. Down-regulation of c-MYC, reduced cell growth, and decreased activity of the PI3K/AKT/mTORC1 signal transduction pathway are features of the terminal differentiation of committed myeloid precursors to polymorphonuclear neutrophils. Since mTORC1 regulates growth, we hypothesized that pharmacological inhibition of mTORC1 by rapamycin may reverse the phenotypic effects of c-MYC. Here we show that granulocytes blocked in their ability to differentiate by enforced expression of c-MYC can be induced to differentiate by reducing exogenous c-MYC expression through rapamycin treatment. Rapamycin also reduced expression of endogenous c-MYC and resulted in enhanced retinoid-induced differentiation. Total cellular c-Myc mRNA and c-MYC protein stability were unchanged by rapamycin, however the amount of c-Myc mRNA associated with polysomes was reduced. Therefore rapamycin limited expression of c-MYC by inhibiting c-Myc mRNA translation. These findings suggest that mTORC1 could be targeted to promote terminal differentiation in myeloid malignancies characterized by dysregulated expression of c-MYC.

Auranofin promotes retinoic acid- or dihydroxyvitamin D3-mediated cell differentiation of promyelocytic leukaemia cells by increasing histone acetylation

BACKGROUND AND PURPOSE

To investigate the molecular mechanism for the effect of auranofin on the induction of cell differentiation, the cellular events associated with differentiation were analysed in acute promyelocytic leukaemia (APL) cells.

EXPERIMENTAL APPROACH

The APL blasts from leukaemia patients and NB4 cells were cotreated with auroanofin and all-trans-retinoic acid (ATRA) at suboptimal concentration. The HL-60 cells were treated with auroanofin and a subeffective dose of 1alpha,25-dihydroxyvitamin D3 (1,25(OH)2 vit D3) in combination. The effect of auroanofin was investigated on histone acetylation at the promoter of differentiation-associated genes and expression of cell cycle regulators.

KEY RESULTS

Treatment with auroanofin and ATRA cooperatively induced granulocytic differentiation of fresh APL blasts isolated from patients and NB4 cells. The combined treatment also increased reorganization of nuclear PML bodies and histone acetylation at the promoter of the RARbeta2 gene. Auroanofin also promoted monocytic differentiation of the HL-60 cells triggered by subeffective concentration of 1,25(OH)2 vit D3. The combined treatment of auroanofin and 1,25(OH)2 vit D3 stimulated histone acetylation at p21 promoters and increased the accumulation of cells in the G0/G1 phase. Consistent with this, the expressions of p21, p27 and PTEN were increased and the levels of cyclin A, Cdk2 and Cdk4 were decreased. Furthermore, the hypophosphorylated form of pRb was markedly increased in cotreated cells.

CONCLUSIONS AND IMPLICATIONS

These findings indicate that auroanofin in combination with low doses of either ATRA or 1,25(OH)2 vit D3 promotes APL cell differentiation by enhancing histone acetylation and the expression of differentiation-associated genes.

Cancer stem cells: implications for the progression and treatment of metastatic disease

Metastasis is the major cause of death for cancer patients with solid tumours, due mainly to the ineffectiveness of current therapies once metastases begin to form. Further insight into the biology of metastasis is therefore essential in order to gain a greater understanding of this process and ultimately to develop better cancer therapies. Metastasis is an inefficient process, such that very few cells that leave a tumour successfully form macrometastases in distant sites. This suggests that only a small subset of cells can successfully navigate the metastatic cascade and eventually re-initiate tumour growth to form life-threatening metastases. Recently, there has been growing support for the cancer stem cell (CSC) hypothesis which stipulates that primary tumours are initiated and maintained by a small subpopulation of cancer cells that possess "stem-like" characteristics. Classical properties of normal stem cells are strikingly reminiscent of the observed experimental and clinical behaviour of metastatic cancer cells, including an unlimited capacity for self renewal; the requirement for a specific 'niche' or microenvironment to grow; use of the stromal cell-derived factor 1 (SDF-1)/chemokine receptor 4 (CXCR4) axis for migration; enhanced resistance to apoptosis and an increased capacity for drug resistance. Therefore, in addition to playing a role in primary tumour formation, we believe that CSCs are also key players in the metastatic process. We will review the current evidence supporting this idea and discuss the potential implications of the CSC hypothesis with regards to experimental investigation and treatment of metastatic disease.

New data with arsenic trioxide in leukemias and myelodysplastic syndromes

Arsenic and its derivatives have been used for medicinal purposes for thousands of years. Arsenic trioxide has demonstrated remarkable activity in the treatment of acute promyelocytic leukemia (APL), for which it can bring about complete remissions (CR) in > 80% of patients with relapsed disease, and molecular remission in 90% of those who enter a CR. Clinical trials have explored its use in the first-line setting and as part of consolidation therapy for de novo APL, for which it appears to provide an event-free and overall survival advantage. Two multicenter trials have examined its use in the treatment of the myelodysplastic syndromes; as a single agent, it yields responses in 20% of patients, and smaller trials have provided evidence for its use in non-APL acute myeloid leukemia populations in combination with other drugs such as gemtuzumab ozogamicin, ascorbic acid, and cytarabine.

Arsenic trioxide inhibits ATRA-induced prostaglandin E2 and cyclooxygenase-1 in NB4 cells, a model of acute promyelocytic leukemia

In acute promyelocytic leukemia (APL), all-trans retinoic acid (ATRA) triggers cell differentiation, while arsenic trioxide (As(2)O(3)) generates partial differentiation and apoptosis. Animal and human studies suggest that newly diagnosed APL patients can be cured using As(2)O(3) combined with ATRA. Cyclooxygenases are involved in prostaglandins and thromboxane synthesis. We have recently demonstrated that ATRA induces cyclooxygenase-1 (COX-1) expression and prostaglandin synthesis in NB4 cells and in blasts from patients with APL. In the present study we investigated the effect of ATRA and As(2)O(3) co-treatment on COX-1 expression and prostaglandin formation and tested the effect of the COX-1/COX-2 nonselective inhibitor indomethacin on cell differentiation. Arsenic treatment of NB4 cells resulted in a partial but significant reduction of ATRA-dependent induction of COX-1 expression and activity. Pretreatment of NB4 cells with indomethacin significantly impaired ATRA/As(2)O(3)-induced differentiation, as assessed by cell morphology, nitroblue tetrazolium test or CD11c expression. PGE(2) reversed the negative effect of indomethacin on differentiation of ATRA/As(2)O(3)-treated NB4 cells. In conclusion, COX-1 contributes to ATRA-dependent maturation of NB4 cells and is affected by As(2)O(3). These results also suggest that nonsteroidal antiinflammatory drugs should be avoided in APL patients treated with the combination of ATRA and As(2)O(3).

Additive effects of PI3-kinase and MAPK activities on NB4 cell granulocyte differentiation: potential role of phosphatidylinositol 3-kinase gamma

PURPOSE

In acute promyelocytic leukemia (APL) the chromosome translocation t(15;17) resulting in the PML-RAR alpha fusion protein is responsible for a blockage of myeloid differentiation. In this study we investigated the expression of different Phosphatidylinositol 3-kinase (PI3K) isoforms during granulocyte differentiation of NB4 cells induced by all-trans-retinoic acid (ATRA), 9-cis-retinoic acid (9cisRA) or retinoic acid receptor (RAR) agonists.

METHODS

NB4 cells were analysed for their ability to differentiate into granulocytic lineage by the use of ATRA, 9cisRA or RAR agonists. Expression of signalling proteins was investigated by western blot and real-time PCR. PI3K activity was determined by in vitro kinase assays.

RESULTS

Co-treatment of NB4 cells with either LY294002 to inhibit PI3Ks or PD98059 in order to suppress MEK activity led to significant reduction of CD11b surface expression during ATRA, 9cisRA or the RAR alpha agonist Ro40-6055 dependent NB4 cells granulocyte differentiation. We also show that only the G-protein coupled receptor activated PI3Kgamma isoform demonstrates up-regulated protein and mRNA expression during myeloid differentiation of NB4 cells via RAR alpha and RAR beta-dependent mechanism. Furthermore, activation of MAPK cascade including phosphorylation of MEK increases during retinoid induced differentiation of NB4 cells. Interestingly, protein kinase assays of immunoprecipitated PI3Kgamma revealed a protein of about 50 kDa that is phosphorylated when NB4 cells were treated with the RAR alpha agonist Ro40-6055.

CONCLUSION

Collectively, our data suggest additive effects of PI3K and MAPK activity on ATRA-dependent NB4 cells granulocyte differentiation.

DNA methylation-independent loss of RARA gene expression in acute myeloid leukemia

The retinoic acid receptor (RAR) α gene (RARA) encodes 2 major isoforms and mediates positive effects of all-trans retinoic acid (ATRA) on myelomonocytic differentiation. Expression of the ATRA-inducible (RARα2) isoform increases with myelomonocytic differentiation and appears to be down-regulated in many acute myeloid leukemia (AML) cell lines. Here, we demonstrate that relative to normal myeloid stem/progenitor cells, RARα2 expression is dramatically reduced in primary AML blasts. Expression of the RARα1 isoform is also significantly reduced in primary AML cells, but not in AML cell lines. Although the promoters directing expression of RARα1 and RARα2 are respectively unmethylated and methylated in AML cell lines, these regulatory regions are unmethylated in all the AML patient cell samples analyzed. Moreover, in primary AML cells, histones associated with the RARα2 promoter possessed diminished levels of H3 acetylation and lysine 4 methylation. These results underscore the complexities of the mechanisms responsible for deregulation of gene expression in AML and support the notion that diminished RARA expression contributes to leukemogenesis.

On the role of transforming growth factor-beta in the growth inhibitory effects of retinoic acid in human pancreatic cancer cells

Background

Retinoids are potent growth inhibitory and differentiating agents in a variety of cancer cell types. We have shown that retinoids induce growth arrest in all pancreatic cancer cell lines studied, regardless of their p53 and differentiation status. However, the mechanism of growth inhibition is not known. Since TGF-β2 is markedly induced by retinoids in other cancers and mediates MUC4 expression in pancreatic cancer cells, we investigated the role of TGF-β in retinoic acid-mediated growth inhibition in pancreatic cancer cells.

Results

Retinoic acid markedly inhibited proliferation of two cell lines (Capan-2 and Hs766T) in a concentration and time-dependent manner. Retinoic acid increased TGF-β2 mRNA content and secretion of the active and latent forms of TGF-β2 (measured by ELISA and bioassay). The concentrations of active and TGF-β2 secreted in response to 0.1 – 10 μM retinoic acid were between 1–5 pM. TGF-β2 concentrations within this range also inhibited proliferation. A TGF-β neutralizing antibody blocked the growth inhibitory effects of retinoic acid in Capan-2 cells and partially inhibitory the effects in Hs766T cells.

Conclusion

These findings indicate that TGF-β can cause growth inhibition of pancreatic cancer cells, in a p53-independent manner. Furthermore, it demonstrates the fundamental role of TGF-β in growth inhibition in response to retinoic acid treatment is preserved in vitro.

PNAS-2: a novel gene probably participating in leukemogenesis

OBJECTIVE

As(4)S(4) is an effective drug for the treatment of acute promyelocytic leukemia but its mechanism of action remains largely unknown. In a previous study, we identified PNAS-2, a human apoptosis-related protein gene, using gene expression profiling. In this study, we tried to clarify the role of PNAS-2 in apoptosis and leukemogenesis.

METHODS

NB4 and U937 leukemia cell lines and serial clinical samples were studied. RNA interference (RNAi) and RNA overexpression were used to address the potential role of PNAS-2 in apoptosis. PNAS-2 expression was examined using Northern blot in multiple tissues, and real-time PCR was applied to analyze PNAS-2 expression in various patient samples.

RESULTS

Functional analyses of PNAS-2 by RNAi and RNA overexpression indicate PNAS-2 is an anti-apoptosis gene. PNAS-2 expression is significantly increased in de novo or relapsed acute leukemia, but in patients in complete remission PNAS-2 levels decrease to levels comparable to those found in normal controls. In carcinomas, PNAS-2 expression was not upregulated, indicating that PNAS-2 overexpression was specific for leukemia.

CONCLUSION

Based on the preliminary data, we suggest that the PNAS-2 gene functions as an anti-apoptotic gene and probably participates in leukemogenesis.

Relationship between the induction of leukemia cell differentiation and the enhancement of reporter gene expression in 3T3 Swiss cells

The histone deacetylase (HDAC) inhibitor trichostatin A (TSA) and hexamethylene bisacetamide (HMBA), which lacks HDAC inhibitory activity, both possess the capacity to induce leukemia cell differentiation and to enhance the expression of a wide range of transiently transfected reporter genes in 3T3 Swiss cells. In addition, known inducers of leukemia cell differentiation, including hypoxanthine, diazepam, 6-thioguanine and phorbol 12-myristate 13-acetate, also exhibited the ability to enhance reporter gene expression, while randomly chosen compounds that did not induce leukemia cell differentiation did not enhance reporter gene expression. The activity of TSA in the transfection system was modified by co-expression of histone acetyltransferase p300 and HDAC1; whereas, that of HMBA was enhanced by co-expression of the TATA-binding protein TBP. The stimulatory effects of diverse chemical inducers on transiently transfected genes suggest the existence of multiple exploitable targets for the selection of novel inducers of differentiation that function as modulators of gene activity.

Treatment of acute promyelocytic leukaemia with all-trans retinoic acid and arsenic trioxide: a paradigm of synergistic molecular targeting therapy

To turn a disease from highly fatal to highly curable is extremely difficult, especially when the disease is a type of cancer. However, we can gain some insight into how this can be done by looking back over the 50-year history of taming acute promyelocytic leukaemia (APL). APL is the M3 type of acute myeloid leukaemia characterized by an accumulation of abnormal promyelocytes in bone marrow, a severe bleeding tendency and the presence of the chromosomal translocation t(15;17) or variants. APL was considered the most fatal type of acute leukaemia five decades ago and the treatment of APL was a nightmare for physicians. Great efforts have been made by scientists worldwide to conquer this disease. The first use of chemotherapy (CT) was unsuccessful due to lack of supportive care and cytotoxic-agent-related exacerbated coagulopathy. The first breakthrough came from the use of anthracyclines which improved the complete remission (CR) rate, though the 5-year overall survival could only be attained in a small proportion of patients. A rational and intriguing hypothesis, to induce differentiation of APL cells rather than killing them, was raised in the 1970s. Laudably, the use of all-trans retinoic acid (ATRA) in treating APL resulted in terminal differentiation of APL cells and a 90-95% CR rate of patients, turning differentiation therapy in cancer treatment from hypothesis to practice. The combination of ATRA with CT further improved the 5-year overall survival. When arsenic trioxide (ATO) was used to treat relapsed APL not only the patients but also the ancient drug were revived. ATO exerts dose-dependent dual effects on APL cells: at low concentration, ATO induces partial differentiation, while at relatively high concentration, it triggers apoptosis. Of note, both ATRA and ATO trigger catabolism of the PML-RARalpha fusion protein which is the key player in APL leukaemogenesis generated from t(15;17), targeting the RARalpha (retinoic acid receptor alpha) or promyelocytic leukaemia (PML) moieties, respectively. Hence, in treating APL both ATRA and ATO represent paradigms for molecularly targeted therapy. At molecular level, ATRA and ATO synergistically modulate multiple downstream pathways/cascades. Strikingly, a clearance of PML-RARalpha transcript in an earlier and more thorough manner, and a higher quality remission and survival in newly diagnosed APL are achieved when ATRA is combined with ATO, as compared to either monotherapy, making APL a curable disease. Thus, the story of APL can serve as a model for the development of curative approaches for disease; it suggests that molecularly synergistic targeted therapies are powerful tools in cancer, and dissection of disease pathogenesis or anatomy of the cancer genome is critical in developing molecular target-based therapies.

RXR is an essential component of the oncogenic PML/RARA complex in vivo

Although PML-enforced RARA homodimerization allows PML/RARA to bind DNA independently of its coreceptor RXR, the latter was identified within the PML/RARA complex. We demonstrate that a PML/RARA mutant defective for RXR binding fails to trigger APL development in transgenic mice, although it still transforms primary hematopoietic progenitors ex vivo. RXR enhances PML/RARA binding to DNA and is required for rexinoid-induced APL differentiation. In RA-treated PML/RARA-transformed cells, the absence of RXR binding results in monocytic, rather than granulocytic, differentiation. PML/RARA enhances posttranslational modifications of RXRA, including its sumoylation, suggesting that PML-bound sumoylation enzymes target RXRA and possibly other PML/RARA-bound chromatin proteins, further contributing to deregulated transcription. Thus, unexpectedly, RXR contributes to several critical aspects of in vivo transformation.

Hematopoietic cell transplantation in acute promyelocytic leukemia: a comprehensive review

The past three decades have brought major therapeutic advances in the management of acute promyelocytic leukemia. The current state-of-the-art induction treatment with all-trans retinoic acid in combination with anthracycline-based chemotherapy results in long-lasting remissions and cure in up to 70% of newly diagnosed patients. Unfortunately, treatment failure still occurs in one-third of patients. When disease relapses, patients can achieve subsequent remissions with arsenic trioxide, all-trans retinoic acid with or without chemotherapy, or other therapies. Patients achieving molecular remissions after salvage therapy are generally considered candidates for high-dose chemotherapy and autologous hematopoietic cell transplantation as a postconsolidation strategy. On the other hand, patients with evidence of persistent hematologic or molecular disease after salvage therapy could be offered allogeneic hematopoietic transplantation if a suitable HLA-donor is identified and the patient's overall performance and clinical condition are permissible. We hereby provide a comprehensive review and analysis of published clinical trials that evaluate the role of hematopoietic cell transplantation across different stages of acute promyelocytic leukemia.

PS-341 or a combination of arsenic trioxide and interferon-α inhibit growth and induce caspase-dependent apoptosis in KSHV/HHV-8-infected primary effusion lymphoma cells

Kaposi's sarcoma (KS)-associated herpes virus (KSHV) is the causative agent of primary effusion lymphoma and of KS. Primary effusion lymphoma (PEL) is an aggressive proliferation of B cells. Conventional chemotherapy has limited benefits in PEL patients, and the prognosis is very poor. We previously reported that treatment of human T-cell leukemia virus type 1 (HTLV-1)-associated adult T-cell leukemia/lymphoma cells either with arsenic trioxide (As) combined to interferon-alpha (IFN-alpha) or with the bortezomib (PS-341) proteasome inhibitor induces cell cycle arrest and apoptosis, partly due to the reversal of the constitutive nuclear factor-kappaB (NF-kappaB) activation. PEL cells also display an activated NF-kappaB pathway that is necessary for their survival. This prompted us to investigate the effects of PS-341, or of the As/IFN-alpha combination on PEL cells. A dramatic inhibition of cell proliferation and induction of apoptosis was observed in PS-341 and in As/IFN-alpha treated cells. This was associated with the dissipation of the mitochondrial membrane potential, cytosolic release of cytochrome c, caspase activation and was reversed by the z-VAD caspase inhibitor. PS-341 and As/IFN-alpha treatment abrogated NF-kappaB translocation to the nucleus and decreased the levels of the anti-apoptotic protein Bcl-X(L). Altogether, these results provide a rational basis for a future therapeutic use of PS-341 or combined As and IFN-alpha in PEL patients.

Is your metabolism determined by (cell) fate?

The rise in the incidence of metabolic disease to become a major public health problem has been met with a substantial increase in research into both the clinical and basic science of metabolism. This work has revealed that the origins of metabolic diseases of adults can begin early in life. Furthermore, the age of onset of symptoms has been rapidly decreasing. Therefore, pediatricians should be critically involved in both the generation of new therapies as well as the institution of measures of disease prevention. This perspective examines how recent advances have improved our understanding of the development of metabolic diseases. A connection between glucocorticoids and the origins of metabolic disease is one enticing clue because of the clinical similarity between patients with glucocorticoid excess and those with metabolic disease. A unifying link was found by investigating the role of glucocorticoids on cell fate and differentiation of mesenchymal stem cells. We conclude that understanding the mechanisms by which glucocorticoids can modify how cell fate decisions are made holds promise for developing new therapies and preventative measures.

Suppressive Effects of Statins on Acute Promyelocytic Leukemia Cells

The family of statins includes pharmacologic inhibitors of the 3-hydroxy-3-methylglutaryl-CoA reductase that are potent regulators of cholesterol biosynthesis. In addition to their cholesterol-lowering effects, statins inhibit cell proliferation and promote apoptosis of malignant cells in vitro, but their potential therapeutic roles in the treatment of malignancies remain to be defined. We examined the effects of statins on the growth and differentiation of acute myeloid leukemia (AML) cells. Atorvastatin and fluvastatin were found to be potent inducers of cell differentiation and apoptosis of the NB4 acute promyelocytic leukemia (APL) cell line. Such effects correlated with activation of the small G-proteins Rac1/Cdc42 and downstream engagement of the c-Jun NH(2)-terminal kinase kinase pathway, whose function was found to be essential for the generation of proapoptotic responses. Importantly, different statins were found to enhance all-trans-retinoic acid (ATRA)-dependent differentiation of APL blasts and reverse resistance to the antileukemic effects of ATRA. In addition, fluvastatin exhibited growth-inhibitory properties on primary bone marrow-derived leukemic progenitors from patients with AML and enhanced the suppressive effects of ATRA on leukemic progenitor colony formation. Altogether, these studies establish that statins exhibit potent antileukemic properties in vitro and raise the possibility that combinations of statins with ATRA may be an effective approach to overcome the development of ATRA resistance by the leukemic cells.

Drug-induced Sweet's syndrome

OBJECTIVE

To systematically review the pertinent literature on drug-induced Sweet's syndrome (SS).

DATA SOURCES

MEDLINE (1966-December 2006), International Pharmaceutical Abstracts (1970-December 2006), Science Citation Index (1945-December 2006), and EMBASE (1980-December 2006) were searched using the key terms Sweet's syndrome, drug-induced, and acute neutrophilic dermatitis.

STUDY SELECTION AND DATA EXTRACTION

All case reports of drug-induced SS located using the above databases were collected for causality assessment. In addition, relevant articles regarding the various causes and presentations of SS were selected to provide background information. Bibliographies of all relevant articles were reviewed for additional citations.

DATA SYNTHESIS

All case reports of drug-induced SS were evaluated against an expanded Naranjo scale with specific criteria for SS. Tables were developed listing key criteria for evaluating the case reports for causality. Data were evaluated by quantity and quality of evidence, and an assessment was made as to whether there was a feasible pharmacologic mechanism to explain causality.

CONCLUSIONS

Granulocyte colony-stimulating factor (G-CSF), all-trans retinoic acid (ATRA), and vaccines met 2 of 3 criteria for an association with SS. There are sufficient data and a plausible pharmacologic mechanism for G-CSF and ATRA. Vaccines meet the qualitative criteria and also have a plausible pharmacologic mechanism. The evidence regarding minocycline is of high quality; however, the quantity of evidence and a reasonable pharmacologic mechanism are lacking. A host of miscellaneous drugs have also been implicated in causing the disorder, all without sufficient evidence.

Combination therapy with arsenic trioxide, all-trans retinoic acid, and gemtuzumab ozogamicin in recurrent acute promyelocytic leukemia

BACKGROUND

From 20% to 30% of patients with acute promyelocytic leukemia (APL) who are treated with all-trans retinoic acid (ATRA) develop recurrent disease. Arsenic trioxide (ATO) is an effective agent for the salvage of patients with recurrent APL, and gemtuzumab ozogamicin (GO) has shown activity in patients with APL.

METHODS

The authors investigated the efficacy of a combination of ATO, ATRA, and GO in 8 patients with APL in first recurrence (7 patients with hematologic recurrences and 1 patient with a molecular recurrence). All patients had received previous treatment with ATRA either alone or in combination with other agents. Patients received ATO 0.15 mg/kg intravenously until they achieved a bone marrow complete remission (CR). Once in CR, patients received consolidation with ATO, ATRA, and GO for 10 months. Patients then received maintenance with idarubicin, ATRA, 6-marcaptopurine, and oral methotrexate for 11 months.

RESULTS

All 7 patients who had hematologic recurrences achieved CR after a median of 39 days (range, 21-56 days). After a median follow-up of >/=36 months (range, 4-55 months), 6 patients remained alive in CR, and 2 patients died in CR. Six of 8 patients remained in second CR that was longer than their first CR. All 7 evaluable patients achieved molecular remission. There were no grade 3 or 4 extramedullary toxicities. Two patients died, 1 secondary to a complication of metastatic lung adenocarcinoma, and the other of sepsis.

CONCLUSIONS

The combination of ATO, ATRA, and GO was effective and may achieve durable remissions in patients with APL in first recurrence. It should be considered as an effective alternative to allogeneic or autologous transplantation.

Implications of cancer stem cells in the treatment of cancer

Identification of cancer stem cells (CSCs) in both hematological and solid malignancies suggests that CSCs may be a common phenomenon for most malignancies. Similarly to normal stem cells, CSCs can self-renew and differentiate into progeny cancer cells. Almost all current therapy against cancer targets differentiated cancer cells. CSCs are more resistant to therapy secondary to quiescence, increased expression of antiapoptotic proteins and drug efflux transporters. In this article, we review the current status of CSC research and propose the targeting of CSC cell-surface molecules, signal transduction pathways, the stem cell niche, stem cell differentiation and drug resistance.

Arsenic trioxide and acute promyelocytic leukemia: clinical and biological

Arsenic has recently been identified as an effective drug in the treatment of newly diagnosed and relapsed acute promyelocytic leukemia. Indeed, arsenic trioxide combined with all-trans retinoic acid shows a synergistic effect. Mechanistically, arsenic targets the key leukemogenic protein PML-RARalpha, setting up a new example of molecular target-based cancer therapy.

Haemostatic problems in acute promyelocytic leukaemia

Despite the development of highly effective treatment strategies for acute promyelocytic leukaemia around 10% of patients die in the presentation period as a consequence of the associated bleeding diathesis. The cause of the coagulopathy is complex resulting from a combination of tissue factor (TF) and cancer procoagulant (CP) induced disseminated intravascular coagulation, exaggerated fibrinolysis due predominantly to enhanced expression of annexin II on APL blast cell membranes and blast cell production of cytokines. All-trans retinoic acid (ATRA) has revolutionised the treatment of APL. When combined with chemotherapy long term survival rates of up to 80% can be achieved. Commencement of ATRA induces APL blast cell differentiation and is associated with a rapid resolution of the bleeding tendency through a combination of effects which include up regulation of thrombomodulin and down regulation of TF and CP production and cell surface expression of annexin II.

Mouse Modeling in Oncologic Preclinical and Translational Research

Through scientific and technological advancements, our ability to manipulate the mouse genome has allowed us to evaluate the effect of specific genetic alterations on in vivo tumorigenesis. This has allowed and will allow us to define molecular pathways describing the processes of tumor initiation, invasion, and progression to metastatic disease. Additionally, these models may serve as an excellent platform for the identification of novel molecular targets for therapy as well as to evaluate the efficacy of targeted therapies. Ultimately this will translate from preclinical mouse model trials to the development of clinical trials and protocols for cancer patients. Here we review the usefulness of mouse modeling in oncologic translational research.

The NPM-RAR fusion protein associated with the t(5;17) variant of APL does not interact with PML

The PML protein localizes to regions of the nucleus known as nuclear bodies or PODs. However, in t(15;17) Acute Promyelocytic Leukemia (APL) blasts, PML is found in a micro-punctate pattern. In order to test the hypothesis that delocalization of PML from PODs is necessary for APL, we investigated the interaction of the t(5;17) APL fusion protein NPM-RAR with PML. NPM-RAR localizes diffusely throughout the nucleoplasm. NPM-RAR does not alter the localization of PML in transfected HeLa cells, and does not associate with PML in vitro. These studies suggest that NPM-RAR does not interact with PML.

Sudden death due to undiagnosed acute promyelocytic leukemia: a case report

Acute promyelocytic leukemia (APL) is associated with severe hemorrhagic coagulopathy induced by the release of procoagulant, plasminogen, and protease from leukemic cells. The case described in this report is of a 15-year-old male who unexpectedly died due to a cerebral hemorrhage caused by underlying APL within 12 h after presentation. This case suggests that underlying APL should be considered as a differential diagnosis when sudden death occurs with a fatal spontaneous hemorrhage, although it is rare.

Isochromosome 1q in a myelodysplastic syndrome after treatment for acute promyelocytic leukemia

A growing body of literature reports therapy-related myelodysplastic syndrome (t-MDS) and acute myeloid leukemia (t-AML) in patients treated successfully for acute promyelocytic leukemia (APL). We report a t-MDS with an isochromosome 1q as a sole abnormality, 47,XY,+1,i(1)(q10), in a 46-year-old man with APL 14 years after he was treated with cytosine arabinosine and daunorubicin. The literature on t-MDS/t-AML after APL therapy and on isochromosome 1q is reviewed.

Acute promyelocytic leukemia and constitutional trisomy 21

The incidence of acute myelogenous leukemia (AML) in patients with constitutional trisomy 21 is estimated to be 1 in 300; it is usually seen before age four. Clinical and epidemiological data confirm the improved life expectancy of patients with Down syndrome and their increased susceptibility to the development of leukemia, among other cancers. The most frequent subtype of AML associated with Down syndrome is acute megakaryoblastic leukemia (FAB: M7). The description of acute promyelocytic leukemia (APL) in adult patients with Down syndrome is exceedingly rare. Herein, we describe the unusual presentation, treatment, results, and clinical course of an adult patient with APL and constitutional trisomy 21 and provide a brief review of the literature.

The estrogen-responsive B box protein is a novel regulator of the retinoid signal

Retinoic acid (RA) induces growth arrest, cell death, and differentiation in many human cancer cells in vitro and has entered routine clinical use for the treatment of several human cancer types. One mechanism by which cancer cells evade retinoid-induced effects is through repression of retinoic acid receptor beta (RARbeta) gene transcription. The RA response element beta (betaRARE) is the essential DNA sequence required for retinoid-induced RARbeta transcription. Here we show that the estrogen-responsive B box protein (EBBP), a member of the RING-B box-coiled-coil protein family, is a betaRARE-binding protein. EBBP undergoes serine threonine phosphorylation and enhanced protein stability after RA treatment. Following RA treatment, we also observed increased nuclear EBBP levels in aggregates with the promyelocytic leukemia protein at promyelocytic leukemia nuclear bodies. EBBP enhanced RA-responsive RARbeta transcription in RA-sensitive and -resistant cancer cells, which were resistant to both a histone deacetylase inhibitor and a demethylating agent. EBBP-specific small interfering RNA reduced basal and RA-induced RARbeta expression. EBBP increased betaRARE-transactivating function through its coiled-coil domain. Taken together, our work suggests that EBBP may have a pivotal role in the retinoid anti-cancer signal.

Anti-leukemic and anti-angiogenesis efficacy of arsenic trioxide in new cases of acute promyelocytic leukemia

Arsenic trioxide is now considered the standard agent in treatment of refractory cases of acute promyelocytic leukemia (APL). This drug is also shown to have anti-angiogenesis effect against APL cells in vitro. This study evaluated clinical efficacy and anti-angiogenesis effect of arsenic trioxide in 17 new cases of APL. Arsenic trioxide was given in a dosage of 0.15 mg kg(-1) and remission rate, survival rate, toxicities and effect on vascular density of bone marrow was studied. The bone marrow vascular density was examined using immunohistochemistry for von Willebrand Factor (vWF) and CD31 markers. Bone marrow vascular density was determined by calculating mean vessel number in 3 hot spot, high power microscopic fields. Bone marrow vascular density was reduced as identified by anti-vWF immunohistochemical staining (Mean before treatment = 201.6 mm(-2) +/- 20.4 (SEM), mean after treatment = 109.4 +/- 17.2 (SEM), p < 0.001) and anti-CD31 immunostaining (mean before treatment = 199.17 mm(-2) +/- 21.5 (SEM), mean after treatment = 99.5 mm(-2) +/- 22.1 (SEM), p < 0.05). Treatment efficacy results showed 100% complete remission rate after median of 30 days and 72% survival rate after median 860 days of follow-up. Main toxicities included hyper-leukocytosis, hepatic toxicity and APL differentiation syndrome. The results imply that arsenic trioxide is an effective anti-leukemia and anti-angiogenesis agent in new cases of APL.

Retinoic acid metabolism blocking agents (RAMBAs) for treatment of cancer and dermatological diseases

The naturally occurring retinoids and their synthetic analogs play a key role in differentiation, proliferation, and apoptosis, and their use/potential in oncology, dermatology and a variety of diseases are well documented. This review focuses on the role of all-trans-retinoic acid (ATRA), the principal endogenous metabolite of vitamin A (retinol) and its metabolism in oncology and dermatology. ATRA has been used successfully in differentiated therapy of acute promyelocytic leukemia, skin cancer, Kaposi's sarcoma, and cutaneous T-cell lymphoma, and also in the treatment of acne and psoriasis. However, its usefulness is limited by the rapid emergence of acquired ATRA resistance involving multifactoral mechanisms. A key mechanism of resistance involves ATRA-induced catabolism of ATRA. Thus, a novel strategy to overcome the limitation associated with exogenous ATRA therapy has been to modulate and/or increase the levels of endogenous ATRA by inhibiting the cytochrome P450-dependent ATRA-4-hydroxylase enzymes (particularly CYP26s) responsible for ATRA metabolism. These inhibitors are also referred to as retinoic acid metabolism blocking agents (RAMBAs). This review highlights development in the design, synthesis, and evaluation of RAMBAs. Major emphasis is given to liarozole, the most studied and only RAMBA in clinical use and also the new RAMBAs in development and with clinical potential.

A unique case of acute promyelocytic leukemia showing monocytic differentiation after ATRA (all-trans retinoic acid) therapy

Acute promyelocytic leukemia (PML) is characterized by a reciprocal translocation between chromosomes 15 and 17 resulting in a chimeric PML and retinoic acid receptor alpha (RARA) oncogene. The resultant fusion protein (PML/RARA) is thought to block differentiation of bone marrow cells arrested at the promyelocytic stage. In vitro and in vivo studies have shown that the large majority of APL cells undergo granulocytic maturation after ATRA therapy. We report a unique case of a PML/RARA positive APL patient exhibiting extensive monocytic differentiation after ATRA therapy as documented by morphology, flow cytometry, and FISH studies. We discuss potential dual capability for granulocytic/monocytic differentiation of PML/RARA positive APL cells and implications of monocytic differentiation in the management of APL patients treated with ATRA.

PLC-β2 monitors the drug-induced release of differentiation blockade in tumoral myeloid precursors

The differentiation therapy in treatment of acute promyelocytic leukemia (APL), based on the administration of all-trans retinoic acid (ATRA), is currently flanked with the use of As2O3, a safe and effective agent for patients showing a resistance to ATRA treatment. A synergy between ATRA and As3O3 was also reported in inducing granulocytic differentiation of APL-derived cells. We have demonstrated that phospholipase C-beta2 (PLC-beta2), highly expressed in neutrophils and nearly absent in tumoral promyelocytes, largely increases during ATRA treatment of APL-derived cells and strongly correlates with the responsiveness of APL patients to ATRA-based differentiating therapies. Here we report that, in APL-derived cells, low doses of As3O3 induce a slight increase of PLC-beta2 together with a moderate maturation, and cooperate with ATRA to provoke a significant increase of PLC-beta2 expression. Remarkably, the amounts of PLC-beta2 draw a parallel with the differentiation levels reached by both ATRA-responsive and -resistant cells treated with ATRA/As2O3 combinations. PLC-beta2 is not necessary for the progression of tumoral promyelocytes along the granulocytic lineage and is unable to overcome the differentiation block or to potentiate the agonist-induced maturation. On the other hand, since its expression closely correlates with the differentiation level reached by APL-derived cells induced to maturate by drugs presently employed in APL therapies, PLC-beta2 represents indeed a specific marker to test the ability of differentiation agents to induce the release of the maturation blockade of tumoral myeloid precursors.

Serum-dependent expression of promyelocytic leukemia protein suppresses propagation of influenza virus

The rate of propagation of influenza virus in human adenocarcinoma Caco-2 cells was found to negatively correlate with the concentration of fetal bovine serum (FBS) in the culture medium. Virus replicated more rapidly at lower FBS concentrations (0 or 2%) than at higher concentrations (10 or 20%) during an early stage of infection. Basal and interferon (IFN)-induced levels of typical IFN-inducible anti-viral proteins, such as 2',5'-oligoadenylate synthetase, dsRNA-activated protein kinase and MxA, were unaffected by variation in FBS concentrations. But promyelocytic leukemia protein (PML) was expressed in a serum-dependent manner. In particular, the 65 to 70 kDa isoform of PML was markedly upregulated following the addition of serum. In contrast, other isoforms were induced by IFN treatment, and weakly induced by FBS concentrations. Immunofluorescence microscopy indicated that PML was mainly formed nuclear bodies in Caco-2 cells at various FBS concentrations, and the levels of the PML-nuclear bodies were upregulated by FBS. Overexpression of PML isoform consisting of 560 or 633 amino acid residues by transfection of expression plasmid results in significantly delayed viral replication rate in Caco-2 cells. On the other hand, downregulation of PML expression by RNAi enhanced viral replication. These results indicate that PML isoforms which are expressed in a serum-dependent manner suppress the propagation of influenza virus at an early stage of infection.

MNU-induced carcinogenesis of rat mammary gland: effect of thyroid hormone on expression of retinoic acid receptors in tumours of mammary gland

The rat model of N-methyl-N-nitrosourea (MNU)-induced mammary carcinomas is well-established animal model for breast cancer. This study was carried out to investigate whether hypothyroid (thyroidectomy or PTU treatment) or hyperthyroid status of female rats would affect MNU-induced mammary carcinogenesis with specific focus on both retinoid and rexinoid receptor expression in mammary tumours. Application of PTU before and during MNU-induced mammary gland carcinogenesis yielded in a marked decrease of the number and volume of tumours per animal, however, there was no effect of hypothyroid state in thyroidectomized rats as well as hyperthyroid state concerning the number and volume of tumours. Mammary tumours of in euthyroid group of MNU animals showed that there was no tumour, in which all of subtypes of retinoid and rexinoid receptors were expressed. A different pattern of expression of retinoid or rexinoid receptors was found either in MNU-induced mammary carcinomas in both hypothyroid and hyperthyroid rats.

Individualised cancer therapeutics: dream or reality?

Traditional measures for treating metastatic cancer involve identification of the originating organ from which the neoplasm arose and empirical treatment with cytotoxic chemotherapy. Arguably, with the exception of haematological malignancies, demonstration of efficacy in solid tumours has been limited. Over the past half-decade, theoretical and technological advances have resulted in greater application of molecular science to drug design, which has enabled development of new 'targeted' therapeutics. However, generic chemotherapy paradigms have not changed. Establishment of the optimal population for 'targeted' therapeutics based on molecular diagnostics (i.e. genomic and proteomic characterisation) to identify sensitive tumour-host ecosystems in individual patients at the 'bedside', is not being done as part of routine oncology management. This review focuses on the concept of designing individualised therapeutics based on genomic and proteomic profile of malignant tissue. Genetic and epigenetic perturbations in signal pathways drive cancer growth, survival, invasion and metastatic spread. The burgeoning evidence which supports the concept that each patient's cancer has a unique complement of pathogenic genetic and molecular derangements is reviewed. Such evidence supports the strategy of individualised selection of a therapeutic complex from a menu of targeting options that best complements the specific oncomolecular profile of the 'tumour-host' system.

Regulation of hematopoiesis by retinoid signaling

The discovery that retinoic acid efficiently stimulates the terminal differentiation of granulocytic leukemia cells had a major impact on clinical hematology, but has also inspired research into the normal function of the retinoid signaling pathway during hematopoiesis. New animal models and loss-of-function approaches have successfully revealed requirements for the pathway at defined embryonic stages that are relevant for distinct hematopoietic cell populations. For example, novel insight has been gained regarding the function of retinoids in yolk sac hematovascular development, fetal erythropoiesis, T-cell homing, and hematopoietic stem and progenitor cell biology. The lessons learned so far indicate that future development of sophisticated animal models will be needed to fully understand the intricacy and specificity of this complex signaling pathway, but that this effort will be productive and continue to inform both basic and clinical research on many fronts.